1. Field of the Invention
The present invention relates to a system for sequentially feeding different kinds of liquid substances in such a manner that after the feeding of a given kind of liquid substance has been completed, the system is switched over to feed the next kind of liquid substance. More particularly, the present invention pertains to such a system capable of sequentially feeding two or more kinds of liquid substances having different properties without causing any changes in flow rate and pressure of the liquid substance being fed even when the system is switched over to feed the different kinds of liquid substances.
2. Description of the Prior Art
In general, when two or more kinds of liquid substances having different properties are sequentially fed, they are changed over from a given kind to the next kind of liquid substance before the latter is introduced into supply means to feed the liquid substance from the supply means into a system by means of a delivery pump. Alternatively, a plurality of supply means are provided upstream of a delivery pump, and a valve or the like provided between the supply means and the delivery pump is operated to change over the liquid substances from their one kind to the next kind. In such a method, however, when a changeover to the second liquid substance is made, the second liquid substance passes through the same delivery pump as that for the liquid substance fed before the changeover. For this reason, particularly when the changeover is effected between liquid substances having different properties, e.g., from one with a low viscosity to another with a high viscosity, from one including solid matter to another not including such matter, and vice versa, the resistance to passage of the liquid substance through the pump may vary, or there may be a change in the slip amount of the liquid substance between the rotor and stator of the pump, or the pump may be clogged with the solid matter at the clearance therein, resulting in undesirably large changes in flow rate and pressure of the liquid substance being fed after changeover.
The above problems are often encountered, particularly when it is necessary to apply a high pressure into the system. Moreover, it is extremely difficult in any attempt to prevent the occurrence of the above-mentioned problems and to adjust the delivery rate and pressure of the pump within a very short period of time and with a high accuracy when the liquid substances are changed over, due to the limited ability of the delivery pump and a lag time from when the changes in the delivery rate and pressure of the pump are detected to the time when a proper control thereof is effected.
Further, in the case where a liquid food or pharmaceutical is to be sterilized to a sufficient extent that it is microbiologically safe, that is, where a liquid substance is to be fed into a sterilizer at a predetermined flow rate and pressured and processed in the sterilizer at a constant residence time and temperature of the liquid substance, the above-mentioned problems may result in such disadvantages as sterilization failure due to insufficient heating of the liquid substance or deterioration in quality due to overheating thereof. Further, particularly, in the case where a liquid substance is processed by an aseptic processing system, there may be an occurrence of the intrusion (contamination) of germs into a sterile zone on the downstream side of the sterilizer, resulting in a fairly serious problem.